R1287x Series PWM/ VFM, Dual-channel Step-up/ Inverting DC/DC Converter with Synchronous Rectifier for LCD NO.EA-325-180907 OUTLINE The R1287x is a PWM/ VFM dual-channel step-up/ inverting DC/DC converter with synchronous rectifier for LCD. The step-up DC/DC converter (CH1) generates a 4.5 V to 5.8 V boosted output voltage and the inverting DC/DC converter (CH2) generates a 4.5 V to 6.0 V inverting output voltage. Internally, the R1287x consists of an oscillator circuit, PWM control circuits, a reference voltage unit, error amplifiers, soft-start circuits, a LX peak current limit circuit, short protection circuits, thermal shutdown circuit, an under voltage lockout circuit (UVLO), a NMOS transistor driver and a synchronous PMOS transistor driver for CH1, and a PMOS transistor driver and a synchronous NMOS transistor driver for CH2. The R1287x is employing synchronous rectification for improving the efficiency of rectification by replacing diodes with built-in switching transistors. Using synchronous rectification not only increases circuit performance but also allows a design to reduce parts count. The R1287x provides the PWM control or the PWM/VFM auto switching control. The PWM control switches at fixed frequency rate in low output current in order to reduce noise. Likewise, the PWM/VFM auto switching control automatically switches from PWM mode to VFM mode in low output current in order to achieve high efficiency. RICOHs unique control method can suppress a ripple voltage in the VFM mode, thus the R1287x can achieve both low ripple voltage at light load and high efficiency. Both CH1 and CH2 can independently control the ON/ OFF control and freely set the starting sequence and shutdown sequence. Both CH1 and CH2 own an auto-discharge function which actively discharges the output voltage to ground when the device is placed in shutdown mode. The R1287x is offered in a 12-pin WLCSP-12-P1 package and a 12-pin DFN3030-12 package. FEATURES Operating Voltage Range 2.5 V to 5.5 V Step-up DC/DC Converter (CH1) Selectable Step-up Output Voltage (VOUTP) R1287xxxxy: 4.5 V to 5.8 V (0.1 V Step) Step-up Output Voltage (Externally adjustable) R1287x001y: 4.5 V to 5.8 V Maximum Output Current (Dependent on inductance) R1287xxxxB/D/F/H: 200 mA, R1287xxxxC/G: 100 mA Inverting DC/DC Converter (CH2) Selectable Inverting Output Voltage (VOUTN) R1287xxxxy: 4.5 V to 5.8 V (0.1 V Step) Inverting Output Voltage (externally adjustable) R1287x001y: 4.5 V to 6.0 V Maximum Output Current (dependent on inductance) R1287xxxxB/D/F/H: 200 mA, R1287xxxxC/G: 100 mA 1 R1287x NO.EA-325-180907 Controller ON/ OFF Control: Operates CH1/ CH2 separately by the EN1/ EN2 pin. Auto-discharge Function: Discharges the output voltage to GND within a short time in shutdown mode. Latch-type Short Circuit Protection: Short-circuiting of either one of CH1 or CH2 activates this circuit. Maximum Duty Cycle L Peak Current Limit Function X Undervoltage Lockout (UVLO) Threshold Typ. 2.25 V Thermal Shutdown Temperature Typ. 150C Oscillator Frequency R1287xxxxB/D/F/H:1 MHz, R1287xxxxC/G: 300 kHz Package WLCSP-12-P1, DFN3030-12 APPLICATIONS Power source for hand-held equipment Power source for LCD 2